what to do w/set of 5s on river?

[cd1680]

Full Tilt Poker - No Limit Hold'em Cash Game - $0.25/$0.50 Blinds - 5 Players - (LegoPoker HH Converter)

SB: $49.50
<font color="black">Hero (BB): $99.05</font>
UTG: $54.15
CO: $48.70
BTN: $405.25

<font color="black">Preflop:</font> Hero is dealt 5[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/club.gif[/img] (5 Players)
2 folds, BTN calls $0.50, SB folds, Hero checks

<font color="black">Flop:</font> ($1.25) 5[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/diamond.gif[/img] 2[img]/images/graemlins/spade.gif[/img] (2 Players)
Hero checks, BTN checks

<font color="black">Turn:</font> ($1.25) T[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $1.25</font>, <font color="red">BTN raises to $2.50</font>, <font color="red">Hero raises to $8.75</font>, BTN calls $6.25

<font color="black">River:</font> ($18.75) 8[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $10.50</font>, <font color="red">BTN raises all-in to $396.00</font>, Hero ?????

opponent is 88/26/0.88 over 270 hands